Move RDJSON rendering to `ruff_db` (#19293)
## Summary
Another output format like #19133. This is the
[reviewdog](https://github.com/reviewdog/reviewdog) output format, which
is somewhat similar to regular JSON. Like #19270, in the first commit I
converted from using `json!` to `Serialize` structs, then in the second
commit I moved the module to `ruff_db`.
The reviewdog
[schema](https://github.com/reviewdog/reviewdog/blob/320a8e73a94a09248044314d8ca326a6cd710692/proto/rdf/jsonschema/DiagnosticResult.json)
seems a bit more flexible than our JSON schema, so I'm not sure if we
need any preview checks here. I'll flag the places I wasn't sure about
as review comments.
## Test Plan
New tests in `rdjson.rs`, ported from the old `rjdson.rs` module, as
well as the new CLI output tests.
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Co-authored-by: Micha Reiser <micha@reiser.io>
